I've learned to handle it
I've modified my long message twice now, and when it takes long to modify, you have to connect to get it through, but somehow after a long break the connecting takes too much time, after which java script error appears. So it's better to make the connection first from another window, and then click the 'send message' button.
I've copied the edited message, too, to avoid losing it altogether (then I can paste it into the message field, but that's complicated). The surest way is to connect from another place (Favourites) first, as you, billectric, did.